Allegro 5 api
#include <allegro5/allegro.h> size_t al_utf16_width(int c)
Returns the number of bytes that would be occupied by the specified code point when encoded in UTF-16. This is either 2 or 4 bytes for legal code point values. Otherwise returns 0.
al_utf16_encode(3alleg5), al_utf8_width(3alleg5)